Vista is definitely worth it, if you have the specs, OR if you know how to configure your computer to maximize the performance. Using 3 Gigs of virtual memory on each of your hard drives and plugging in flash drives to count as RAM would definitely help Vista work well.
I have not yet encountered ANYTHING that does not work with vista except Paretologic Antispyware. All games I have work, all software works (assuming you have the latest version of the software).
For games, Vista also has DirectX 10, which works WONDERS for the gaming type of person. The graphics quality amazes me.
If you have a lower-end computer, you can install Windows Basic. If that still doesn't help, you can just reduce the menus to look like "windows classic", which will allow you to keep all the great things that makes programs run well on Vista, but increase the speed. Of course, I ALWAYS recommend maximizing the capabilities of your computer with better hardware, so when you do that, you can upgrade, and that's fine. It's better to cope with XP while you build up for the perfect comptuter.
Other perks of Vista: Audio mixer (to change the volume of each specific applitcation), thumbnail taskbar (see a small picture of what is minimized when scrolling over the taskbar), Halo 2 (duh), automatic driver updates (EVERYTHING I have ever attached to this computer had its drivers found by Vista's Window's Update without a problem), great look (obviously, the interface and flow of everything looks much more beautiful and smooth), faster boot time (I'm not sure if others can testify for this, but Vista starts up SO much faster for me than XP did), Windows Defender (spyware protection for those too cheap to buy other brands), and other things I can't think up at the moment.
I hope that helped =)
~~Ben